Intravascular blood filter

ABSTRACT

Disclosed is a novel filter and delivery means. The device described within will not interfere with standard practice and tools used during standard surgical procedures and tools such as cannulas, clamps or dissection instruments including valve replacement sizing gages or other surgical procedures where the patient must be put on a heart-lung machine cross-clamping the aorta.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/838,949, filed Dec. 12, 2017, which is a continuation of U.S.application Ser. No. 13/738,847, filed Jan. 10, 2013, which is acontinuation of U.S. application Ser. No. 12/689,997, filed Jan. 19,2010, now U.S. Pat. No. 8,372,108, which claims priority benefit under35 U.S.C. sctn. 119(e) to U.S. Provisional Application No. 61/145,149,filed Jan. 16, 2009, entitled “Intravascular Blood Filter,” all of whichapplications are hereby incorporated by reference in their entirety.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

BACKGROUND OF THE INVENTION

This invention relates generally to medical devices used during vascularintervention, and more particularly, concerns medical devices that areuseful in treating aortic valve replacement, thromboembolic disordersand for removal of foreign bodies in the vascular system.

Thromboembolic disorders, such as stroke, pulmonary embolism, peripheralthrombosis, atherosclerosis, and the like, affect many people. Thesedisorders are a major cause of morbidity and mortality in the UnitedStates and throughout the world. Thromboembolic events are characterizedby an occlusion of a blood vessel. The occlusion can be caused by a clotwhich is viscoelastic (jelly-like) and is comprised of platelets,fibrinogen, and other clotting proteins.

Percutaneous aortic valve replacement has been in development for sometime now and stroke rates related to this procedure are between four andtwenty percent. During catheter delivery and implantation plaque may bedislodged from the vasculature. The invention contained within willblock the emboli from traveling through the carotid circulation and ontothe brain. When an artery is occluded by a clot, tissue ischemia (lackof oxygen and nutrients) develops. The ischemia will progress to tissueinfarction (cell death) if the occlusion persists. Infarction does notdevelop or is greatly limited if the flow of blood is reestablishedrapidly. Failure to reestablish blood-flow can lead to the loss of limb,angina pectoris, myocardial infarction, stroke, or even death.

Occlusion of the venous circulation by thrombi leads to blood stasiswhich can cause numerous problems. The majority of pulmonary embolismsare caused by emboli that originate in the peripheral venous system.Reestablishing blood flow and removal of the thrombus is highlydesirable.

There are many existing techniques employed to reestablish blood flow inan occluded vessel. One common surgical technique, an embolectomy,involves incising a blood vessel and introducing a balloon-tipped device(such as a Fogarty catheter) to the location of the occlusion. Theballoon is then inflated at a point beyond the clot and used totranslate the obstructing material back to the point of incision. Theobstructing material is then removed by the surgeon. While such surgicaltechniques have been useful, exposing a patient to surgery may betraumatic and is best avoided when possible. Additionally, the use of aFogarty catheter may be problematic due to the possible risk of damagingthe interior lining of the vessel as the catheter is being withdrawn.

A common percutaneous technique is referred to as balloon angioplastywhere a balloon-tipped catheter is introduced into a blood vessel,typically through an introducing catheter. The balloon-tipped catheteris then advanced to the point of the occlusion and inflated in order todilate the stenosis. Balloon angioplasty is appropriate for treatingvessel stenosis but is generally not effective for treating acutethromboembolisms.

Another percutaneous technique is to place a microcatheter near the clotand infuse Streptokinase, Urokinase, or other thrombolytic agents todissolve the clot. Unfortunately, thrombolysis typically takes hours todays to be successful. Additionally, thrombolytic agents can causehemorrhage and in many patients the agents cannot be used at all.

Another problematic area is the removal of foreign bodies. Foreignbodies introduced into the circulation can be fragments of catheters,pace-maker electrodes, guide wires, and erroneously placed embolicmaterial such as thrombogenic coils. There exist retrieval devices forthe removal of foreign bodies, certain of such devices form a loop thatcan ensnare the foreign material by decreasing the size of the diameterof the loop around the foreign body. The use of such removal devices canbe difficult and sometimes unsuccessful.

Moreover, systems heretofore disclosed in the art are generally limitedby size compatibility and the increase in vessel size as the emboli isdrawn out from the distal vascular occlusion location to a more proximallocation near the heart. If the embolectomy device is too large for thevessel it will not deploy correctly to capture the clot or foreign body,and if too small in diameter it cannot capture clots or foreign bodiesacross the entire cross section of the blood vessel. Additionally, ifthe embolectomy device is too small in retaining volume then as thedevice is retracted the excess material being removed can spill out andbe carried by flow back to occlude another distal vessel.

Various thrombectomy and foreign matter removal devices have beendisclosed in the art. However, such devices have been found to havestructures which are either highly complex or lacking in sufficientretaining structure. Disadvantages associated with the devices havinghighly complex structure include difficulty in manufacturability as wellas difficulty in use in conjunction with microcatheters. Recentdevelopments in the removal device art features umbrella filter deviceshaving self folding capabilities. Typically, these filters fold into apleated condition, wherein the pleats extend radially and can obstructretraction of the device into the micro catheter sheathing.

What has been needed and heretofore unavailable is an extraction devicethat can be easily and controllably deployed into and retracted from thecirculatory system for the effective removal of clots and foreignbodies. There is also a need for a system that can be used as atemporary arterial or venous filter to capture and remove thromboemboligenerated during endovascular procedures. Moreover, due todifficult-to-access anatomy such as the cerebral vasculature and theneurovasculature, the invention should possess a small collapsed profileand preferably be expandable to allow the device to be delivered throughthe lumen of commercially available catheters. The present inventionsatisfies these needs.

SUMMARY OF THE INVENTION

Most filter devices are delivered from the groin and are placed distalto the flow of the lesion or site in question. Single basket-typefilters or Nitinol loop filters are the most common used today incarotid stent procedures of vein graft stenting. As the guidewire isdelivered past the lesion the filter is delivered over the guidewireprotecting the distal vasculature. The invention here may be deliveredfrom the groin in a conventional manner to vessels such as the carotidarteries or via radial (arm vasculature) approach. Protecting thecarotid arteries and cerebral vasculature system is the main goal whileleaving the aortic arch free from catheters and wire as much as possibleduring the delivery of other devices such as aortic balloons andprosthetic valves or other associated devices.

One method of filtering the carotid arteries leaving the aorta free fromobstruction is to deliver a filter to each of the carotid arteries fromthe groin leaving them in the carotid vasculature and retrieving themvia snare post procedure. A delivery catheter would be inserted throughan introducer in the groin (femoral artery) and delivered to the commoncarotid arteries and detached. The delivery catheter would be removedand a second filter would be delivered in a similar manner to the othercarotid artery. With two detached filters now in place the proceduretreating the aortic or mitral valve can now be completed with embolicprotection for the cerebral vascular system. Once the procedure to thevalve is completed, the filters can be snared and retrieved back out thefemoral artery as they were delivered. Any embolic particles will becaptured in the filter device and removed safely from the body.

Another method for filtering the carotid arteries would be to deliver afilter from the femoral artery and utilize a single catheter to housethe two attachment means to the filters. These attachments may be a wiresimilar to a guidewire or a hypo-tube to connect the filter element toan external portion of the body. Keeping these wires or connection meansorganized and contained within a single or dual lumen catheter will helporganize and limit potential entanglement with other catheters beingdelivered to the target site such as the aortic valve or other cardiacelements including but not limited to the mitral valve and coronaryarteries. The distal portion of the catheter may have a single exitportion or a staggered exit to allow an exit at different points alongthe catheter. One exit port may be at the distal most end of thecatheter and the other may be a centimeter proximal from this to allowthe attachment wire to exit near the left common carotid artery.Furthermore, there could be an extension to the distal most portion ofthe catheter allowing side ports for both wires to exit. This wouldallow for additional catheter stabilization within the aorta.

Another embodiment would deliver filters to the carotid from the radialartery and allow for a clear aortic arch from catheters and otherdelivery means from a more conventional femoral delivery means. Fromthis access site a plurality of filters could be delivered through acommon access sheath or the filters could be delivered from a dual lumencatheter with each lumen housing a single filter.

Another delivery means would utilize a single catheter with filtersmounted in a coaxial manner where the distal filter would be deliveredfirst and could be mounted to a wire where the second would be mountedto a hypo-tube where the first filters wire would run through the secondallowing for relative motion between the two filters. The first filterwould be delivered to the left common carotid from the radial artery andthe second would be delivered to the right common carotid artery or thebrachiocephalic trunk in a coaxial manner. These filters would beopposed in direction as the distal filter would be filtering bloodflowing from the base of the aorta to the head and toward the distal endof the guidewire. The proximal filter would be filtering blood from thebase of the aorta to the head and toward the proximal end of theguidewire. Placing the two filters together there would be a conicalshape configuration where the large diameter portions of the cones wouldmeet. These two filters would be delivered in a collapsed configurationand expanded when expelled from the delivery catheter. Retrieval wouldbe a retraction of the filter back into a recovery catheter that wouldbe a larger inner diameter than the delivery catheter to allow room forparticulate. Being opposed in capture direction the right carotid wouldbe the first filter that would be recovered by an expanded sheath wherethe embolic material would not be disturbed and further withdrawn to asmaller sheath for removal from the body. The expanded sheath could beconstructed from braided Nitinol wire pre-shaped so when exposed thebraid would expand to receive the filter without squeezing out anytrapped emboli. The second or left carotid filter would be recovered ina conventional manner where the larger diameter would be pulled into asheath to trap and remove the emboli within the tailor distal portion ofthe filter.

Another means to deliver the filters via radial artery approach would beto utilize a dual lumen catheter where each lumen would house a singlefilter. The first lumen would deliver a filter to the left carotidartery and the second lumen would deliver a filter to the right carotidartery. The lumens could be staggered in length to reach each ostium inwhich case the first or left filter lumen would be longer in length toallow for placement distal from the second filter placement in the rightcarotid. Additionally, the second lumen may be pre-shaped with a curveto allow easy access to the right carotid artery. This pre-shaped curvemay be retained in a straighter manner to allow for delivery andreleased to express the delivery shape when at the bifurcation of thesubclavian and the carotid artery. Furthermore, there may be an activeshaping where the curve is directed external to the body by a handlemechanism such as a pull-wire where tension would generate a compressiveforce to the catheter column preferentially bending the lumen. Recoverycould utilize the same dual lumen concept or utilize a second recoverysheath independently from one another.

Another application for this device and method would be for surgicaloperations where the patient may be put on heart-lung bypass. Duringcross clamping of the aorta catheters or wires in the aorta mayinterfere with the procedure and allow leakage of blood around thecannulas used. If any of the above described devices or techniques areused before the patient's chest is opened this filtration of the carotidvessels would protect from emboli thus reducing the stroke risk duringand after the procedure. Additional anti thrombotic coatings to thefilter could allow for an extended implantation time allowing filtrationtime to be extended post procedure. An example of this coating would beHeparin. Placement of these catheters and filters could be underfluoroscopy or ultrasound guidance to direct proper filter placement.Radiopaque markers may add necessary visibility to the catheter, filterand or wires.

Another surgical delivery means would be an insertion to the carotidartery via the neck. The filter could face either antigrade orretrograde depending upon the placement insertion point or access site.This would allow for complete filtration without any aortic interferenceas the entire devices would be within the carotid circulation. With thisdelivery technique the puncture site would be very small and recoverycould be through the entry site or through the groin as the filter couldbe inserted distal to meet a recovery sheath in the aorta. With thisgroin recovery any emboli within the proximal carotid would be capturedbefore later dislodgement.

Intravascular filters have been used in many configurations ranging froma windsock style as commercialized as the FilterWire from BostonScientific or the ACCUNET from Abbott Vascular or the Spider from eV3.These filters utilize a memory metal such as Nitinol is used to opposethe vascular wall tightly sealing any emboli from passage while a filtermaterial such as a porous fabric material retains and emboli frompassing distally from the device. Another example is a laser cut memorymetal where the basket is the frame and the filter is used to trapemboli when expanded. Another example is constructed from a braided wiresuch as Medtronic's Interceptor PLUS where once exposed the braidexpands to create a funnel or cone shape to trap emboli and the proximalor larger end is pre-shaped to accept blood flow with larger openingsheat-set into the memory metal such as Nitinol. These filters range indiameter from about 2-15 mm in diameter and are approximately 20-30 mmin length. They are generally attached to a guidewire and sheathed fordelivery and resheathed for recovery. The catheter profile measuresabout 1 to 2 mm in diameter and has a length of about 90 to 200 cm.Catheter construction is normally a polypropylene or polyethylenematerial but nylons and blends can be used as well. All devices areconsidered single use and are commonly placed for carotid stenting orsavenous vein grafts stenting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the vascular anatomy of the aorta and surroundinggreat vessels.

FIG. 2 illustrates the common technique in carotid filter 8 insertionfor carotid stenting 10 as delivered via femoral artery over a guidewire9.

FIG. 3 illustrates the aortic vasculature where sheaths could be placedby the interventional cardiologist. The right femoral 11 being the mostcommon access as the cardiologist works from the right side of thepatient which is presented to the physician while on the table. Theright radial artery 12 has been used but due to the small diameter ofthe vessel is not a common insertion point for the cardiologist.

FIG. 4 illustrates a brachial entry with common introducer 13 andguidewire 8 techniques.

FIG. 5 illustrates the guide catheter 14 being inserted to theintroducer 13 over the guidewire 8 in a brachial artery entry where theguide catheter 14 has a preshaped distal section to access the leftcommon carotid 3.

FIG. 6 illustrates a closer view of the guide catheter 14 and guidewire8 accessing the left carotid artery where the first filter would beplaced.

FIG. 7 illustrates the deployment of the first filter 9 through theguide catheter 14 over a guidewire 8 where the filter 9 is fully opposedto the left carotid artery.

FIG. 8 illustrates both filters 9 deployed and protecting the carotidarteries utilizing a common guidewire 8 and common guide catheter 14.

FIG. 9 illustrates a dual lumen catheter 29 where each filter 9 has asingle guidewire 8. Both filters 9 are in a conventional orientationwhere the flow is in the distal direction or toward the distal tip ofthe guidewire 8. Independent recovery of the filters 9 could occur or acommon recovery sheath may be used to load both into one sheath.

FIG. 10 illustrates both filters 9 being delivered via subclavian wherethe left filter is delivered via left subclavian artery with an entrypoint in the radial artery. Each delivery would include a guidewire 8and a guide catheter 14 where a pre-shaped curve would allow access intothe respective carotid artery.

FIG. 11 illustrates a single organization catheter 15 to retain twofilter 9 guidewires 8 controlling the potential for entanglement witheach wire or other catheters introduced to the body. These catheterswould include pigtail catheters used for contrast injections, ballooncatheters for dilation or other catheters for delivery of therapeuticagents or implantable devices such as stents or prosthetic heart valveswhere the catheters are generally larger (18-26 French) in diameter. Thecatheter would have two distal exit ports to allow each filter to exitat the respective ostia. A distal section would extend beyond thebrachiocephalic trunk allowing for a smooth shape to the catheter andensure it is close to the outer radius of the arch.

FIG. 12 illustrates a dual lumen catheter 16 with an active curvingmechanism to steer each lumen to the respected carotid artery. Thedeflection will allow for active steering of each distal section toaccount for any differences in anatomy from patient to patient. Similarto electrophysiology catheters a deflection wire 18 could be tensionedto provide a bias or curve to tip. The delivery of each filter would bein a conventional orientation where the blood flow would be in thedistal direction and toward the tip of the guidewire. External to thebody would be a handle mechanism 17 providing an actuation force to thedistal portion of the catheter. This actuation could be a rotationalknob 19 translating a rotation movement to a screw mechanism providing atension to a wire connected to the catheter tip. Other methods couldinclude an electrical signal to drive a motion or hydraulic actuation totranslate a force.

FIG. 13 illustrates a filter 9 delivered over the guidewire 8 from thecarotid artery in a retrograde approach just short of the aortic arch.Once the procedure is completed the filter can be snared with aconventional snare 20 to remove it from the body. This will allow for avery small (0.03 inch) entry port in the neck to introduce the deviceand a larger recovery sheath 21 in the groin where other devices areintroduced.

FIG. 14 illustrates a set of filters in the carotid arteries deliveredand ready for additional procedures to occur under filtered protection.During a percutaneous heart valve delivery there may be multiplecatheters in the aortic arch consuming much of the available area. Shownhere is a pigtail catheter 22 and a delivery catheter 24 for apercutaneous heart valve 23 all within the aortic arch. The filters 9are clear of the aortic space and will not interfere with delivery orwithdrawal of these catheters.

FIG. 15 illustrates another delivery pathway for the placement in thecarotid or brachiocephalic trunk. Delivery includes a guidewire 8introduced via carotid artery or subclavian artery just short of theaortic arch leaving the arch free from interference while deliveringother catheters to the heart. These filters 9 can be retrieved eitherthrough the groin or recovered back through the entry point in thecarotid or subclavian artery.

FIG. 16 illustrates a conventional entry to the carotid artery where thesheath is placed in a retrograde manner. A sheath 13 is placed into thecarotid artery where access may be gained to the vasculature either antigrade or retrograde depending upon the desired placement of the device.

FIG. 17 illustrates an example of a common filter design where theguidewire 8 passes through the central portion of the filter 27. Amemory material such as Nitinol is used to expand the filter material tothe vessel wall.

FIGS. 18A-B illustrate other examples of filters where a loop style 25has the guidewire passing along the side of the device and functionslike a wind-sox when deployed in the vessel. The other example is aframed filter where when expanded the filter material is opposed to thevessel wall and the guidewire 8 passes through the central portion ofthe device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Before standard intervention would occur by a cardiologist a filterwould be placed into the carotid arteries to protect the circulation tothe brain where emboli could induce a stroke and leave the patientdebilitated. Placement of these filters to the patient's carotidcirculation would be most convenient if it occurred without obstructionof the aorta where other catheters would be passed and preferably on thepatient's right side as it is common practice for the doctor to steerthe catheters from this side of the table. Standard practice is to gainaccess in the right femoral artery where a sheath would be placed tointroduce catheters, guidewires and other device delivery means. Thiswould leave the left femoral artery open but often it too is used forother diagnostic catheters and it is less convenient to work across thepatient's body. Other access sites would include carotid entry but theneck area is often again inconvenient to operate from and generally toofar from the other wires and catheters. The final entry point would bean arm entry where a sheath would be placed into the brachial or radialartery for access to the subclavian artery and more distally the aortaand the carotid arteries. This approach would allow the doctor to accessthe patient's right arm placing a sheath into the radial artery anddelivering catheters, guidewires and sheaths to the carotid arteries.After a 5 French sheath placement a guide catheter would be placed intothe radial artery and advanced to the brachiocephalic trunk where theright carotid artery meets the subclavian. From here a curve in theguide catheter would allow a 180 turn to occur accessing from thebrachiocephalic trunk into the aortic arch and back up the left carotidartery which is commonly found one centimeter down the aortic arch. Oncethe guide catheter is place a filter may be advanced into the leftcarotid artery and deployed leaving this vessel protected from emboli.The guide catheter could be moved proximally to leave this vasculatureand back into the brachiocephalic trunk artery where a coaxial filtercould now be placed protecting this carotid artery. The connectionbetween the two filters is a common axial link where the distal or leftcarotid filter would be attached to a 0.014 inch guidewire as normallyconstructed and the more proximal filter would utilize a tubular membersuch as a polymer or Nitinol hypo tube. The distal filter may need to begently engaged to the vessel wall to allow the connection guidewire tobe tensioned removing any slack or loop within the aortic arch. This maybe possible with engagement barbs restricting proximal motion of thedevice in the vessel when deployed. Other means may be a stronger forcein the memory metal loop to keep the device opposed to the wall. Now thecirculation to the brain is protected and the aortic arch is clear fromobstruction the normal procedure can occur. Examples of these proceduresinclude but are not limited to: [0042] Coronary stenting [0043] Aorticvalve replacement via catheterization [0044] Aortic or mitral valvereplacement via transapical [0045] Aortic balloon valvuloplasty [0046]Mitral valvuloplasty [0047] Mitral valve replacement via catheterization[0048] Diagnostic catheterization [0049] Surgical valve replacement(aortic or mitral) [0050] Surgical valve repair (aortic or mitral)[0051] Annuloplasty ring placement [0052] Atrial fibrillationcatheterization [0053] PFO closure (surgical or catheter based) [0054]Left atrial appendage closure (catheter or surgical)

Once the procedure has been completed the filters may be removedimmediately or left in place if an antitrombotic coating is added or thepatient remains on blood thinning agents to limit clot from forming onthe filters. It may be advantageous to leave the filters in for a periodof twenty four hours as the patient begins to recover. When removal isnecessary the goal is to not dislodge any trapped emboli within thefilter. Conventionally this is accomplished by pulling the filter into alarger recovery sheath to first close the open end of the filter anddraw the remaining portion safely back into the recovery catheter. Withthe filters being opposed in direction it may be advantageous to movethe distal filter into the proximal filter and recover them bothtogether in a nested orientation.

What is claimed: 1) A method of preventing foreign material fromtraveling into the carotid circulation, the method comprising: advancinga first filter system through a right subclavian artery, the firstfilter system comprising a first guide catheter and a first filter;expanding the first filter in a first vessel; advancing a second filtersystem through a left subclavian artery, the second filter systemcomprising a second guide catheter and a second filter; and expandingthe second filter in a second vessel.